Aminoindane amides as well as the processes for the preparation thereof have been widely reported in the prior art, such as in JP1070479, JP1117864, JP1313402, JP2157266, JP2249966, JP3077381, JP62096471, EP199822, EP256503, EP276177, EP280275, EP569912, U.S. Pat. No. 5,093,347, WO01/53259, WO2004/018438, WO2004/039789, WO2004/072023, WO2004/103975, WO2005/075452, WO2012/084812 and WO2013/186325.
In particular, WO2013/186325 discloses that the compound 3-difluoromethyl-N-(7-fluoro-1,1,3-trimethyl-4-indanyl)-1-methyl-4-pyrazolecarboxamide can be prepared in four steps starting from 4-fluoroaniline and acetone. These two compounds are first condensed together to form a substituted dihydroquinoline, which is then hydrogenated to afford the corresponding tetrahydroquinoline. The tetrahydroquinoline is then reacted with a pyrazole carboxylic acid derivative and the resulting compound is subjected to acid rearrangement to provide the corresponding aminoindane amide derivative. The 4-step preparation is reported below in Scheme 1.

However, said process is not satisfactory since from a chemical point of view, the secondary amine in the tetrahydroquinoline ring is quite difficult to acylate; therefore, forcing reaction conditions such as addition of an excess of a base and the use of a chlorinated organic solvent are needed so as to obtain the corresponding acyl tetrahydroquinoline. Moreover, the overall yields of this process are relatively low and lead to a significant loss of the pyrazole acid chloride derivative, which is an expensive material.
It is also known that 4-aminoindane derivatives can be used as key intermediates for synthesizing aminoindane amide derivative. An example of such a synthesis can be found in EP199822, which discloses that aminoindane amide derivatives can be obtained through a condensation reaction between a pyrazole carboxylic acid halide and a 4-aminoindane derivative, as reported below in Scheme 2.

However, in EP199822 there is no indication about the synthetic pathway for preparing the 4-aminoindane derivative.
Few prior art documents actually describe a process for the preparation of such 4-aminoindane derivatives.
For example, EP654464 discloses that 4-aminoindane derivatives in diastereoisomerically-enriched form can be obtained in four steps, as reported in Scheme 3: i) condensation between a dihydroquinoline and a carboxylic acid derivative bearing both a chiral center (indicated with * in the scheme below) and a terminal leaving group LG; ii) catalytic hydrogenation to provide the corresponding tetrahydroquinoline; iii) addition of a strong acid to obtain the corresponding 4-aminoindane derivative; and iv) hydrolysis of the amide bond.

However, the above-mentioned process for the preparation of the 4-aminoindane derivatives is not satisfactory from an industrial point of view, since it requires to use a different solvent for each step (i.e. tetrahydrofuran, methanol and sulphuric acid+water+acetic acid in Example 1, Route N. 1, page 9). Therefore, additional operations are to be performed at the end of any single reaction step in order to avoid for instance, contamination of the subsequent reaction mixture by a remaining chemical or solvent.
Moreover, the acyl dihydroquinoline and the corresponding tetrahydroquinoline are scarcely soluble in apolar solvents, such as aliphatic hydrocarbons. Consequently, in order to completely convert the acyl dihydroquinoline into the corresponding tetrahydroquinoline, higher reaction temperatures or dilution of the reaction mixture are required.
It is therefore desirable to provide an easier process for preparing aminoindane derivatives, in particular aminoindane amides on a large scale, which would reduce costs and production times.